The present invention relates to clamping mechanisms for securing together multiple tubes together in a mutually parallel arrangement, and a method incorporated for use with such mechanism, and more particularly, provides a new and useful structure that can avoid incorporation of guide protrusions, external C-clamps, and the like and at the same time accommodate single-person installation.
Most power plants use steam turbines to generate electricity. A simple steam turbine power plant consists of a boiler, a steam turbine, and a condenser. Water is heated in the boiler to form steam, which is then ducted to the turbine. The turbine converts the steam""s thermal energy to rotational energy, which is used to power an electric generator. The steam exhausted form the turbine is condensed to water in the condenser, and returned to the boiler where it is again converted to steam. Steam power plants can be fueled by nuclear energy or by any conventional fuel that will supply sufficient heat to the boiler. As petroleum supplies dwindle and the environmental consequences of atomic energy use become increasingly evident, the use of coal-fired power plants will, no doubt, increase. Fuel-burning steam turbine power plants typically feature boilers having an array of metal boiler tubes therein. In order to maintain the tubes in an order arrangement and to prevent them from warping if hot spots occur, or if one or more of the boiler tubes springs a leak, it is common to clamp multiple the tubes in an essentially parallel arrangement. Heretofore, many different types of clamping mechanisms have been utilized. Typically, such clamping mechanisms are comprised of a pair of mating half-clamps, which incorporate guide protuberances and cooperating apertures which aid in bringing the tubes into a proximate, mutually parallel configuration. External C-clamps are sometimes provided to pull the half-clamps together, thereby forcing the tubes into the desired parallel configuration. Installation of such clamps often requires the effort of two or more workmen.
U.S. Pat. No. 5,083,372 to Polutnik, et al. discloses a now-common, self-aligning, boiler tube clamp having parallel mating half-clamps. The half-clamps are pulled together with bolts. U.S. Pat. No. 5,060,810 to Jones discloses a similar clamping device for holding load braces on a trailer or truck structure when not in use.
Boiler tubes and the clamps which hold them in parallel configurations are subjected to amazingly harsh environments. Both the tubes and the clamps are generally fabricated from stainless steel. The ranks of boiler tubes are generally positioned vertically within a boiler chamber that is at least several stories high. For coal-fired plants, pulverized coal is introduced into an air stream, ignited as it enters the top of the boiler chamber, and exhausted as ash, carbon dioxide, water vapor and other combustion gases at the bottom of the chamber. The coal dust and coal ash are abrasive, and over time, will erode unprotected materials in the boiler chamber. Those portions of the boiler tube clamp assemblies which project a flat surface perpendicular to the air stream become coated with ash and are, thus, protected against abrasion. However, portions of the clamp assemblies which are not coated, and which are directly exposed to the burning coal dust and coal ash will erode. Surfaces of welds, bolts and nuts which are exposed to the air stream are vulnerable. If welds bolts and nuts, which are used to hold the tube clamps together, project laterally from the sides of the clamps into the air stream, they will weaken from the constant erosion, and will eventually fail.
What is needed are boiler tube clamp assemblies which are generally immune from the erosive action of the coal dust and coal ash when placed within the air stream of a boiler chamber.
The present invention is an improved boiler tube clamp, which has greatly improved immunity to erosion caused by the continual blast of burning coal dust and coal ash in a boiler. Like the boiler tube clamp of Polutnik, et al., the new clamp includes a pair of mating half-clamps having multiple opposed recesses sized to snugly cradle boiler tubes of a given diameter. The half-clamps are brought together around a plurality of boiler tubes, and fastened together either with bolts or welds so as to maintain the tubes in a parallel configuration. Several embodiments of the improved clamp are disclosed. For each embodiment, at least one fastening means is protected from erosion caused by the continual blast of burning coal dust and coal ash. All embodiments feature weldable tabs on generally planar horizontal surfaces which are perpendicular to the flow of the burning coal dust and coal ash. Coal ash, which builds up on the horizontal surfaces, protects the welds from erosion.
A first embodiment of the new clamp mechanism includes a pair of non-matching half-clamps, one of which is equipped with a plurality of slots along the upper and lower surfaces thereof. The other half-clamp is equipped with tabs which mate with the slots of the other half-clamp when both halves are brought together by tightening the screw-type fasteners. The mating locations are readily accessible, thereby allowing a weld to be placed at the junction of each slot and its mating tab. When welds are applied to the new clamp, the clamping function is unaffected by vibration. The new clamp also differs from that of Polutnik, et al. in that provision for installation of a screw-type fastener is made between each adjacent pair of tube recesses. In order to reduce the number of personnel required to install the new clamp, one of the mating half-clamps is equipped with bolt head socket at each bolt insertion location, thereby eliminating the need to hold the bolt head with a wrench while tightening a threadably-attached nut.
A second embodiment of the new clamp is similar to the first embodiment thereof, with the exception that there are no bolt holes in the half-clamps, and no bolts are used to hold to two halves together. The half-clamps are drawn together using some other clamping means and welds are used to hold both half-clamps together.
A third embodiment of the new clamp includes a pair of matching half-clamps, each of which is equipped with a plurality of tabs along the upper surface thereof and a plurality of slots along the lower surface thereof. One half-clamp may be inverted and positioned opposite another so that the tabs of each mate with the slots of the opposing half-clamp. Rather than using a socket recesses on one of the half-clamps to retain the bolt heads of the clamping screw-type fasteners, the head of each bolt may be prevented from rotating by utilizing a locking clip beneath the head of each bolt. A ganged clip may secure all bolts installed in a half-clamp, or individual clips may be employed to lock each bolt to the half-clamp.
A fourth embodiment of the new clamp is similar to the third embodiment thereof, with the exception that there are no bolt holes in the half-clamps, and no bolts are used to hold to two halves together. The half-clamps are drawn together using some other clamping means and welds are used to hold both half-clamps together.